Multiplex modulation communication system



ly'performed-by other equipment. v

1 time division m ulti Unikd State Patent '0 r The invention relates-tomultiplex communication systerns and, particularly, :to a time divisionmultiplex modulation. system usingmagneticcores' and transistors to'perform functions. previously "performed byother equipment. 1

Multiplex communication systems now available require the use ofcomplicated circuits including expensive tator is usually provided atthe transmitting end to sequentially turn onorsample a'. plurality ofmodulator stages. A dilferent source of signal energy isindividually'connected to each of the modulator stages. As eachmodulator stage is turned on by the commutator, a-mod ulated outputsignal is produced in a desired manner-by the modulator stage accordingto the signal energy applied to the modulator stage during thesampling-interequipment such-as vacuum tubes, electronic and mechanicalcommutators or distributors, and so on. A commu- Beftented rea -1e, 1960"ice 2. I the receiving end by magnetic core and transistor cir cuits.

I Still another object is to provide a time division multiplexmodulation communication system which is more compact in constructionand simpler in operation than the time division multiplex modulationcommunication systems now known. V I V According to the invention, atransistorized magnetic core ring counteris provided at the transmittingend or a time division multiplex modulation communication system.Separate sources of tone or voice modulating signal energy areindividually coupled to all but one of the magnetic cores in the ringcounter The ring counter functions:in each-cycle of operation-to"first'pro'duce a, marker or synchronizing signal and to, thereafter,sample the modulating signal energy'supplied by first one'and thenanother of the sources. 'As the modulating signal energy supplied byeach' -source, is sampled,a modulated output signal is produced, themodulated output signal being-determined in a desired manneraccordingto. the modulating signal energy occurring during. the samplinginterval. The marker signal and the sequentially pro.- duced modulatedoutput signals are fed from the ring counter to a common output circuit.The common output circuit functions to combine'the marker signal and Imodulated output signals for {transmission iov'er a single Icommunication path in multiplex fashion. .A .feature.of

the invention is the use of a trarisisjtorized, magnetic core ringcounter-to perform both the-modulating, and commutating functions at thetransmittingend" of agtime iii-1 vision multiplex modulation"communication system;

val. Theq'output circuits of. the respective modulator V 7 stages areall connected to a common output circuit so that the modulated outputsignals produced sequentially by the modulatorstages and originatingoverseparate channels are made available for transmission. over a singlecommunication path inm-ultiplex fashion. The communication path mayincludea radio frequency or other known transmission system.

The multiplex signal is. received at the receiving end of thecommunication system and fed to a suitable commutator. The commutatorfunctions to distribute the modulated signals included in the multiplexsignal over separate paths or channels to different demodulator stages.The outputs of the demodulator stages are fed to utilization circuits.

. Multiplex communication systems of the type described require the useof both communicating and channel modulating equipment at thetransmitting end. The modulator stages, demodulator stages andcommutators used in such systems tend to be expensive to construct andmaintain in terms of the number and type ofcomp'onents used and theresulting power consumption. In addition, the size, weight and number ofcomponents required create problems in the design. and packagingof.equipmentincluding such communication systems The size and weight(or.portability) of the eq'uipmentis of 'par-' ticular concern whenincluded in' telemetering and 'similar; system s.

It is an object of'the-invention to" provide an improved multiplexcommunication system." i

A further objectis to prov1de..a noveltime division multiplex modulationcommunication system using magnetic cores and tr'ansistors :to performfunctions previous- 7 Another object is to obtain a nov v V I V plexcommunication system in which" the commutating mutating anddemodulating'functions are performed at kThe. multiplex signal isreceived atthe receiving end of'the communication system and isfed to. acircuitim eluding a transistorized"magnetic core shift. register. Themagnetic core shift register is operated in synchronism with theoperation of'the ring counter'by means of the marker signals todistribute or direct the modulated signals included in the multiplexsignal over separate channels to 'difierent demodulator stages. 7 j

- .In the particular application of the invention to be described, thering counter at the transmitting end of the. communication systemoperates as apulse positionmodulation' system, whereby the time of each.of the modulated signals produced in the'manner described is variedaccording to the amplitude of the modulating signalen ergy during thesampling interval. Each of the demodulator stagesincludes a transistorbistable multivibrator and a low-pass filter. The multivibrators eachfunction in response to the pulse position modulated signals and inresponse to the marker signals received to produce pulse. widthmodulation signals. A signal which is representative of themodulatingsignalenergy originally supplied. by a corresponding one of the sourcesat the transmitting end of the communicationsystem is derivedfor ap-.plication to a utilization circuit by feeding the pulse width modulationsignals through the low-pass filterQf By means of the invention, a timedivision multiplexj modulation communication system is provided whichis. compact in construction, low in power consumption and readilyadaptable for use in systems where size and weight 1 V of the equipmentare important factors. V

' scribing the operation of a pulse'positio n modulation:

system usingmagnetic QOICS; a

' "Figure 3 'is', a transistor'ize'd magneticicore ring copnter. T'

used accordingto the invention atthetran smittin'g end:

A more detaileddescription of the invention .williiovig fi be given inconnection vwiththe accompanying drawing. inwhich: i a

Figure 1 FigureZf are waveftdrms' useful of a pulse positionmodulationfltime division multiplexit communication system;

Figure 4 is a series. of waveforms useful in describing I the operationof the arrangement shown in Figure 3;

Figure 5 shows one embodiment of a magnetic core commutator andtransistoriz'ed demodulator arrangement used according to the inventionat the receiving end of a pulse position modulation, time divisionmultiplex commnui tio ys Figure 6 is a series of waveforms useful indescribing the operation of the arangement shown in Figure 5;

Figure 7 shows a further embodiment of a magnetic core commutator andtransistorized demodulator arrangeinept used according to the inventionat the receiving end of a pulse position modulation, time'divisionmultiplex communication system; and

Figure 8 shows a series of waveforms useful in describing the operationof the arrangement shown in Figure 7.

Atypical method of generating a time modulated pulse in a positionmodulation system is shown in Figure 1.

waveshape having a linear rate of rise, such. as a sawtooh a isimpressed upon a circuit which generates a pulse at time t when e,reaches some comparison bias level such as E If the positive modulatingvoltage e is added to the sawtooth voltage, it is seenthat the resultantvoltage e +e will reach the comparison bias IE at an earlier time tSimilarly, if e were negative, the resultant of e -l-e would equal E, ata time later than t Thus, as e varies in accordance with the incomingintelligence, the instant at which e +e reaches comparison level, andtherefore the time of occurrence of'the pulse, varies accordingly."Figure 2 shows how a magnetic core with a substantially rectangularB(flux density)-H(magnetizing force) curve can be used as a comparatorfor time modulation. The "distinguishing feature of the material used inthe magnetic core is the abrupt increase (or decrease) in B when" themagnetizing force exceeds a threshold value Hg (or H This phenomenon maybe used to produce pulse position modulation. The operationandconstruction of. magnetic cores per se is known in the art and adetailed description thereof is unnecessary. A magnetic core is acircuit element having a'substantially rectangular hysteresis loop of.low coercive force. Certain materials such as molybdenum periii'alloyand zinc-manganesemagnesium ferrite exhibit a :l bsta'ntiallyrectangular hysteresis loop. A magnetic core'iscapable of beingmagnetized to saturation in either. one of two directions. In onedirection, a positive or active state is said to arise in which thedirection of retentivity is opposite to that which would result from theapplication of a shift or sensing pulse to the magnetic core. In thesecond direction, a negative or inactive state is said to arise in whichthe direction of retentivity is the same as that which would result fromthe application of a shift pulse to the magnetic core.

"A magnetic core in the active or positive state is said to contain aone, and a magnetic core in the negative or inactive state is said tocontain a zero. When a magnetic core is shifted from an active state to.an inactive state, a voltage is induced in an output winding on the coreresulting in a current flow through the output winding of one polarity.A voltage is induced in the output winding on the core when the magneticcore is shifted from an inactive to an active state such that a currentof the opposite polarity. flows through the output winding. The polarityof the current flow through the output winding will in each case dependupon the direction in which the output winding is wound on the core.

In the example given in Figure 2, a sawtooth shaped current i flowsthrough a winding on the magnetic core. When the current i increasesto'the, value shown at t at which time. it produces amagnetomotiveforceH there is' 'avery large increase in flux in themagnetic core.' The. resulting'increase'in voltage induced in any of thewindings'on the magnetic core may be 'us'ed to 'trigger, for

example, a pulse generator. If a modulating signal current flows throughanother winding on the magnetic core, the net magnetizing force is theresultant of that due to the sawtooth current i (times the number ofturns through which it flows) and that due to the modulating current(times the number of turns through which it flows). If the modulatingsignal current i is of the opposite polarity to the current i theresultant magnetizing force l I (the algebraic sum of i,,+ i is reachedat a time 1 which is later than the time t occurring in the case of nomodulation. If the modulating signal current i',, is of the samepolarity as the current it, the resultant magnetizing force H, (thealgebraic sum of i,,+i is reached at a time 't which is earlier than thetime t Thus, the time at which the magnetic core changes state,producing a voltage change in 'a winding and," as a result, a signal forapplication to a utilization circuit, can be advanced or retarded as afunction of the amplitude of a modulating signal. The time displacementwill be linearly related to the modulating voltage if the leading edgeof the sawtooth is reasonably linear over the region of interest. If anon-linear relation between time and modulating. voltage is required, asuitably shaped currentmay be used. v

Referring to Figure 3, a transistorized magnetic core ring counter isshown which is arranged to function as a four-channel pulse positionmultiplex modulation system according to the invention. The ring counterincludes four magnetic cores 10 through 13. A plurality of winding's orcoils are mounted on each of the magnetic cores 10 through 13. Readingin a counter-clockwise direction, the windings are designated as anadvance or trigger winding 14 through 17, an input winding 18 through21, a set winding 22 through 25, a transistor base winding 26 through 29and a transistor collector or output'windin'g 30 through 33,respectively. The advance windings 14,16 on the respective magneticcores 10, 12 are connected in series to an advance pulse generator 34over a lead 35, and the advance windings 15, 17 on the respective mag-'netic cores 11, 13 are connected in series to the pulse generator 34over a second lead 36. The set windings 22 through 25 are connected inseries over an electrical'path including a lead 37, on-oif switch 38, aresistor 39' and a source of unidirectional potential represented by abattery 40. As shown in the drawings, the set winding 22 is wound on themagnetic core 10 in a direction opposite to that in which the setwindings 23 through 25 are wound on the magnetic cores 11 through 13,respectively. .The number of turns for each winding on the magneticcores may, of course, be determined by known means andv procedures. Inan application of the invention which has been constructed, thefrequency of the generator 34 was set so that each magnetic core channelwas. sampled. at a 10 kilocycle rate for voice transmission. A peaksawtooth current of 30 milliamperes was chosen. The advancewindings 14through 17 each had 5 turns, the input windings 18 through 21 each had 5turns, the set windings 22 through 25 each had 20 turns, the basewindings 26 through 29 each had 20 turns and the collector windings 39.through 33 each had 20 turns. In practice, the sampling may occur at alower frequency rate as. used for telemetering andat higher rates asused for program transmission or other higher frequency applications.The values given above by way of example may be determined in aparticular application according to the core material used, currentrequired to switch the core, and so on. The current fed through theadvance windings 1.4 through17 to, switch the cores should be half thatofpeak sawtooth current in order to obtain a maximum of y me rical m dua pa ility- A separate P-N-P junction transistor of N type. con;

ductivity is regeneratively connectedtoeach ofthe mag:

45 are eac arranged to be normall n cond this; 9 l is netic cores 10throughf13. Thetransisto'rs fl through,

However, other types ofv P-NfP junction transistors of v N typeconductivity may be used without the spirit of the invention. a

departing from a In order to provide a ring counter according to the finvention, the output winding on each of the magnetic cores 10 through13 is. connectedtothe'input winding on'the succeeding magneticcore.--,.. Thus, the end of the output winding 30 on the magnetic core10 opposite to theend thereof connected to the collector electrode ofthe transistor 41 is connected to one end of the input remaining state;p

The advance pulse generator 34. functions to supply a first train 63 ofadvance pulses over lead 35 to :the series connected advance windings14,16 and to supplyva'second t'rain 64 of advance pulses over lead 36.to the seriesconnected-advance windings 15, 17. The pulses suppliedvover the respective leads35, 36occur at the. samerate of repetition orfrequency. However, the pulses supplied .ov'eroneof the leads aredelayed,,for example, .a half.

period with respect to the pulses supplied over the other lead-. Theseparation or phasing of the two advance pulse trains 63, 64 can beother than one-half period or one-.. hundred andeighty degrees as longas'the advance pulse e trains, are not coincidental. The pulsessuppliedover the f leads 35, 36 by the pulse'generator 34 have aunidirec:

winding 19 on the next'magnetic core 11, the other end of the inputwinding 19 being connected to ground. The tern ground, as used in thespecification, is to be under stood as referring to a point of fixed orzero alternating current reference potential. :Theoutput winding 31 onthe magnetic core 11 is connected to the input winding 29 on themagnetic core 12 and theoutput winding 32' on the magnetic core 12 isconnected to the input wind- 7 ing 21 on the magnetic core 13 in asimilarmanner. The output winding 33 on the' last. magnetic c0re113in-the chain is connected .tothe input-winding 1 8 on the firstmagneticicore 10 over a-lead 46 also in a similar manner.

. Separate sources ofzmodulating signal energy represented in thedrawing by the blocks 47 through 49 and designated as signalgeneratorsare individually coupled to the magnetic cores 11 through 13viatwindings 50 through 52, respectively. The signal generators 47respective magnetic cores 10 through 13 in a'direction through 49 may beof any suitable type knownin' the I art and may be designated toproducesignal energy in the form of voice, tone or other intelligence.The collector'electrodes of the transistors 41 through 44 are connectedover separate leads 53 through 56 toa common output circuit including aresistor 57 connected to ground and an output terminal 58.; A separatediode or unidirectional current conducting device 59 through 62isconnected in each of the leads 53 through 56, respectively. The diodes59 through 62 are poled in the proper direction such that the modulatedoutput signals produced in a manner to be described are applied inmultiplex fashion to the output terminal 58 for application over a.single communication path to a utilization circuit which may include aradio frequency transmitter or similar equipment. 7 a

In the operation of the ring counter shown in Figure 3, the normallyopen switch 38 is first closed. This action completes an electrical pathfrom battery through the series connected set windings 22 through 25.The set windings 23 through 25 are wound on the magnetic cores 7 11through 13, respectively, in such a direction that the voltage inducedin the set windings 23 through 25 causes the respective magnetic cores11 through 13 to each assume a zero state. 'If .oneror more of'themagnetic previously pointed out, the set winding 22 is wound ontransistor 41 to cause the transistor 41 to conduct. The

current flow through the collector winding 30 causes, due to thedirection in whichthe collector winding 30 themagnetic core 10 in adirectioniopposite'to the direc I tion in which the set windings 23throu'gh 25 are wound' on the magnetic. cores 11 through 13. The setwinding 22 is wound on-the magnetic core10 insuch a direction that thevoltage induced in the set winding 22 causesthe magnetic core 10 toassume a one state. fIf the magtional waveshape with, for example, a"20microsecond leading or sloping edge. Such a waveshape'may be. ap-

proximated by a triangular, sawtooth, rectified sine wave orothersproperly shaped pulse wave. ,The pulse genera-; tor 34 may be ofany suitable type knownand may, for" example, include a source of sine,or square waves to.

which the necessary delay andwave shaping circuits are connected. I Theadvance windings14 through 17 are wound on'the When the firstadvancepulse of the pulse train 63 is applied to the advancewindings-14and 16,'the status of the magnetic core 12 in a zero state is confirmed.

' Since the magnetic core 10 isin a "one" state, the application of theadvance pulse to the advance winding 14 I causesthe magnetic core 10 tostart to shift into a."zero? state. A negative voltage is induced in thebase winding 1 26. As a result, the emitter electrode becomes sufliciently positive with respect to the base electrode of the is wound onthe magnetic core 10, a more negative volt.- age tobe induced in thebase winding 26, biasingthe base electrode of the transistor 41 morenegative, By

, through'the magnetic core 10 is reduced substantially to zero and thetransistor 41 ceases conducting.

ducting, current flows through the input winding 19 on the next magneticcore 11 in a direction such that the current flowing in the inputwinding 19 by the conduction of the transistor 41 causes the magneticcore 11 to shift into a one state. The single eletcrical condition orone state has, therefore, been shifted from the magnetic core 10 to themagnetic core 11. At the time that the magnetic core 11 changes state,.avoltage isinduced in the base winding 27. However, the base winding 27is wound in such a direction that a positive going voltage is inducedtherein. As a result, transistor42 remains'nonconducting. Thereafter,the first advance pulse of the pulse train 64 is applied from the pulsegenerator.

' toshift into azerq state. 'Transistor 42 conductsgacnetic core 12 isshifted into a fone ;state.1 As-additional advance pulses are applied tothe advance windingsnetic core 10 is already in a one state, the statusthereof a is merely confirmed. Upon the release ofv the sw itch 38, e tae ean? a s l i feeeiat te n h cording to 'there'generative actiondescribed. The magnetic core 11 is shifted into a zero state, and themag 14, 16.0ver lead 35 and to theadvance windings; 15,17 over lead 36in the alternate manner described, the

fone state is advanced from magnetic coreto magneticmagnetic coresllthrough 13 are ina"zero'."

eoro' along the chain/on acontinuous or circulatory basis. A ringcounter or commutating action is therefore produced in that first'oneand then another of the magnetic core-transistor circuits in the chainare placed in operation.

In a time division multiplex system, it is necessary to add asynchronizing signal to the output pulse train so that the commutator ordistributor at the receiving end of the system can operate in the properfrequency and phase with that of the transmitting end. It is customaryto provide a synchronizing signal each frame or cycle. Typical: signalsused for this purpose include (1) a sync pulse of several times greaterduration than the channel or modulated pulses, (2) two signals ofrelatively close spacing; and (3) leaving a suitable gap in the pulsetrain. Anyof' these methods may be used in the multiplex system of theinvention. a

Referring to the magnetic core flu-transistor 41'- circuit, one of themethods of providing a synchronizing signal, the second, is illustrated.Each time the magnetic core is made to change from a one to a zero stateand transistor 41 conducts, a positive pulse will appear at thecollector electrode of transistor 41 for application to the terminal 58over lead 53 and through diode 59 which is poled in the proper directionto pass the pulse. An open circuited delay line 65 is connected to thecollector electrode. A second pulse delayed according to the setting ofthe line 65 is produced following the first pulse and fed to terminal 58over lead 53 and through diode 59. The pair of pulses, therefore,constitute a marker or synchronizing signal. A second way of producingthe double pulse marker signal separated from each other by a fewmicroseconds would be to connect two magnetic core-transistor circuitsin parallel.

The number of turns for the sawtooth winding on one core should be lessthan that of the number of turns for the sawtooth winding on the othercore, thus, delaying the pulse produced by the former core with respectto the pulse produced by the latter.- In any case, each cycle ofoperation of the ring counter is begun by the production of asynchronizing signal through the operation of the first channelincluding magnetic core Iii-transistor 41.

, of pulse 68' is dependent on the number of turns on the.

Assuming that the magnetic core 11 has been placed in a one state, thenext sawtooth applied to' winding 15 will cause the magnetic core 11 tostart to change state. Transistor 42 conducts by the regenerative actiondescribed. In the absence of modulation, the amplitude of the sawtoothcurrent, the number of turns on the associated windings, and the valueof H for the core material used are chosen so that the transistor 42conducts and an output pulse is produced at a time corresponding tohalf" peak sawtooth amplitude. As mentioned, a signal generator 47 iscoupled to the magnetic core-11 via winding 50. The signal energysupplied via ,windingSO-servesto modulate the magnetic core 11 in themanner described in connection with Figure 2. The number of'turns on thesignal winding 50 and the amplitude ofthe-peak signal current are chosenso thata peak positivemodulation signal would advance the output pulseto occur at a time T/ 2 seconds before its unmodulated position, where Tis the time of the sawtooth. A peak negative modulation signal woulddelay the output pulse an equal amount. In other words, the time atwhich the transistor 42. conducts is advanced or retarded according tothe time at which the sum of the S21.

tooth current and modulating'signal equals the magneto motive" force H Apulse which is position or time modulated as a function of" theamplitude of the modulating signal appears at the collector electrode oftransis tor-"42. "This implies modulation with equal amplitudeexcursions from the quiescent state.

Ifit was desired to transmit a function which varied in, only'one'direction; such asavsignal corresponding to the-altitudeof a plane=abovesea level, the parameters of the" channei would be chosen so as topositibn' the output pulse at one extreme of the sawtooth correspond ingto seat level, and at the other extreme for the-high estaltitudeexpected. In the latter case; as in the previous one, the peak-to-peakdeviation cannot exceed T' seconds, It should be noted thatdirectcurrent signals may be transmitted using the system of the invention.The direct current flowing through the modulating signal winding 5%)adds (or subtracts) a fixed magnetomotive force from that produced bythe sawtooth current thus advancing (or delaying) the resultantpulse.

Referring to- Figure 4, waveform 4a illustrates the signal appearing atthe collector electrode of transistor 42. The firstnegative pulse 66' isthat induced in the winding 31 when the magnetic core 11 is shifted froma zero state to a *one state. The transistor 42 does not conductattl'iis time because the" voltage is of the wrong polarity. When themagnetic core 11 is shifted" into a 'zero state, transistor- 42conductsand the positivepulse 67 is produced. The current due to-thispulse also shifts the next magnetic core 12 to'the one state. At thetimeof the negative pulse 68, the magnetic core 12 is shifted intoa zerostate, producing the negative pulse at the collector electrodeoftransistor 42 by the voltage induced in winding Ztli Pulse 67issmaller than pulse 66, since the transistor 42 conducts during" pulse67 and loads down the circuit. The amplitude winding 20' which couplesthe two magnetic cores 11-, 12. Waveform 4b illustrates the signal atthe winding 31 side of the input winding 20 on the magnetic core 1 2."Onlythe pulses 67-, 68' are present, since the pulse 66 can not appearat this pointdue to the open circuit condition of the transistorcollector electrode during the duration of pulse 66. Waveform 40illustrates the signal atthe winding 32 side of the winding 21 on themagnetic core 13, and so on.

The operation of the magnetic core 1-2-transistor'43 circuit or' thirdchannel and of the magnetic core 13'- transistor 44 circuit or fourthchannel is exactly the same as described in connection with the magneticcore 111- transistor 42 circuit. The three modulation channels areoperated in turn to sample during discrete intervals the modulatingsignal energy supplied thereto. chronizing signal appearing at thecollector electrode of transistor 41 and the time modulated signalsappearing sequentially at the collector electrodes of the tram-- sistors42 through 44 are fed over the respective leads 53 through 56 to theterminal 53. The diodes 59- through-62 insure that only the proper pulseis applied from each channel to the terminal 58-. For example, the diode60 will pass only the positive pulse 67 which ismodulated by the secondchannel. Pulse 66 is modulated by the first or synchronizing channel,while pulse 68 is modulated by the third channel including magnetic core12-transistor 43. It is to be noted that pulse 67 is greater at thecollector electrode than at the winding 20, since the impedance at thecollector electrode includes both winding 31- and winding 20. Only thewinding 20 is effective when measuring at the winding'2tl. A multiplexsignal similar to the waveform 69will appear at the terminal 58 for eachcycle of operation of the four-channelmultiplex modulation system. Thedouble marker or commutating function.

Various modificationsmay be made to the arrangement" shown in Figure 3'withoutdeparting from the spirit of the invention. In order to minimizethe number or'wind ingson each magnetic core, the set'winding's' 23through 25 may be used" for modulation purposes in place" 0t". The setwindingsf 22" the windings 50 through ,52. through" 25 connected inseries are.- normally open citof conv'entional design; over anelectri'ca cuited by switch 38 after the ring counter has been startedin operation. Thus, the modulating signal for each magnetic time may beconnected across theiset winding of that particular magnetic core.

. While the diodes 59 through 62 are shown as coupling means, thearrangement shown in Figure 3 could be further simplified by removingleads- 53 through 56 and diodes 59 .through 62. Resistors 70 through 73of suitable value are connected across the input windings 18 through'21,respectively, to the terminal 58, as indicated by the dotted lines. Thepulse 68 will subtract from the pulse 67', described above, but bysuitable choice of turns of the input winding compared to the collectorwinding on the preceding magentic core in the ring counter pulse 68 maybe only or 20 percent as large as pulse 67'. Combining thetwo pulseswill decrease the pulse amplitudeias compar'edztothat obtained withdiodes,.but a. v

functions to feed the signals'included in;the multiplex signaltoutilization circuits.

jOn e embodiment of amagnetic core-transistor distrib uting-demodulatingcircuit ararnged according to the invention is shown in Figure 5 Fourmagnetic cores .84 chain of magnetic cores or magnetic core shiftregister. Each of the mag: netic cores 84 through 87 includes an advanceor shift through 87 are connected toform a winding 88 through 91 and aset winding 92 through 95, respectively. The magnetic cores 84 through86 each include an output or collector winding 96through 98 and a basewinding 99-through 101, respectively. An input winding 102 through 104is mounted on each of the magnetic cores 85 through 87, respectively.

The advance windings 88 through 91 are connected in series to an inputterminal 106 to which the incoming multiplex signal is applied. Aseparate P-N-P junction transistor of N type conductivity isregeneratively connected to each of the magnetic cores 84 through 86.The transistors 107 through 109 are normally nonconducting and may be ofthetype designated as 2Nl05. However, other types of vP-N-P junctiontransistors may be used, depending upon the requirements of a particularapplicae tion. The base electrode of the transistor 107' is connectedthrough the base winding .99 to ground, the emitter electrode beingconnected 'to ground. The collector electrode of the transistor 107 isconnected to ground over an electrical path including the collector Themultiplexsignal is a delay-line 121, a resistor 122 connected to groundand- ,lead1123.' The multivibrators 118, 119 are similar in constructionto the multivibrator 117 shown .in detail. The multivibrator 117includes a pair of P-N-Pfiansistors124, 125 ofN type conductivityinterconnected such that either one of two stablestates maybe obtained.

In one stable state, transistor 124 conducts and transistor" 125 iscut-off. In the second ,stablestate, transistor 125 conducts andtransistor 124 is cut-off. .The operation of such a circuit is known inthe art and need. not be described in detail. As shown in Figure 5, themarker pulse separator 120 is connected over 'lead 123. and

through resistor 142 to the base electrode of transistor 124 orleftfhand side of multivibrator 117.. Thesepaq rator 120 is connectedover lead 123 in the same manner to the left hand side of themultivibrators 118, 119.. The set windings 9 2:through95. are connectedinseries:

across the resistor 122.; I

I A tapping point in the connection between the c,ollec--Z tor winding96 and input winding 102 is connected to the base electrode oftransistor: 125 or :right handside-i of multivibrator 117 over anelectrical path including a diode 126, .resistor' 127 connected to:ground and --re. vsistor 128. In a similar manner, a tapping point inthe connection between the collector winding 97 and input winding 103 isconnected to the right hand side of the multivibrator 118 over anelectrical path including a diode 129 and resistor 1 -connected to,ground. ,A tapping point in the connection between the collector winding98.and the input winding 104'is connected to the righthand side ofmultivibrator-119 over an electrical 'path including diode 131 andresistor 132. While vacu um tube diodes 126, 129 and; 131 are shown, anysuitableunidirectional current conducting device maybe. used Thecollector electrode.of transistor 125 functioning as the outputconnection from the multivibrator 117,

. is connectedto an output terminal 133 over an electrical winding 96,input winding 102 on the magnetic core I and a capacitor 110. A resistor111 is connectedacross,

the input winding 102 and capacitor to the negative terminal of a sourceof, unidirectional potential'repre sented by a battery 112. Thesucceeding magnetic cores in the chain are connected in a similar.manner. "Thus,

the magnetic core 85 is connected to the magnetic core: 86 by a circuitarrangement including transistor 108, the

collectorwinding 97, "input winding 103, resistor 1 13 and capacitor114. The magnetic core 86 is connectedgto'the magnetic core 87 by acircuit arrangementfincluding tra'ng' sist'or 109,--co llectorwinding"98,finput winding 104, re}: sistorarid capacitor 116.

three trans'istor bistable multivibrators .117

path including an isolation circuit 134 and a low-pass filter 135. Theoutput terminal 133 is indicated'aschan nel land may be connected to anysuitable receivingdevice such as a loud speaker or code-recording devicethrough suitableamplifying and signal shaping circuits.

Similarly, the output of multivibrator 118 is connected to an outputterminal 136 over an electrical path including an isolation circuit 137and a low-pass filter 138. The output terminal 136 is indicated aschannel 2. The output of the multivibrator 119 isconnected'toan out.-

put terminal 139 over an electrical path including an isolation circuit140 and a low-pass filter 141, terminal 139 being indicated as channel3.

receiving equipment. The isolation circuits 134, 137

and 1 40may include a single amplifying or coupling stage and functionto prevent the, loading of the multivibrators 117 through 119 by therespective filter circuits.v

J Reference willbe made to thewaveforms givenin Figure 6 in 'describingthe operation of the arrangement of Figure 5. A-multiplex signal 147similar to thesignalf 69; shown inFigure 3 and including ineach frame orcycle a double marker or synchronizing signal followed; by three timemodulated pulses, appears at terminal 106. 5 V The multiplex signal isapplied over one path to the se-- fies-connected advancewindings tttithrough 9 1and over, a secondpath to themarker pulseseparator 120, Theseparator operates in response to the synchronizing signal firstreceived to produce a single pulse of fixed time spacing with respect-tothe synchrcnizingsignal and;

separate 'from the channel pulses. The operation of the. separator-1120will, of course, dependuponthej-type z of synchronizing signal used andniay be constructed in.-

oanyofseveral ways knownin the art. ,If;tlie-synchro- Y IZin J na cqns tiofia san n'zthepu e ima cine including a charging; .QcaPacitor whichisiidischar'gedi r As in the case of terminal'133, the terminals 136,139 maybe connected to a loud speakQ Code recording device or othersuitable pulse; train pennittingthis capacitor to charge-towtwice- Inthe example given, the incoming pulse/train may be fed into an opencircuited delay line of delay time T /2 seconds. Each of the doublemarker pulses, as well as the channel pulses, produces a delayed echo Tseconds later due to reflection from the open circuited far'end of theline. As shown in the waveform 148, the echo from the first marker pulseadds to the second marker pulse arriving T seconds after the first andsubstantially doubles the amplitude of the second pulse. Re flections orechoes of the second marker pulse and channel pulses are also produced Tseconds thereafter. Since no other pulses are presentwhen the lattermentioned echoes and reflections are produced, the original first markerpulse, the reflection of-the original second marker pulse, channelpulses and echoes thereof are allof equal height. An amplitude gatemaybe employed to select or separate the single double amplitude pulse.As shown in waveform 149, a single separated marker pulse appears at theoutput of the separator 12.0. A similar result could be obtained by theuse of an integration circuit.

The advance windings'88- through 91 are all wound on the respectivemagnetic cores 84 through 87 in a direction such that the voltageinduced in the windings by the reception of the marker pulses andchannel pulses causes each of the magnetic cores to assume the zerostate. The separated marker pulse shown in waveform 149 is appliedthrough delay line 121 to the series connected set windings 92 through95. The delay line 121 functions to delay the application of theseparated markor pulse to the set windings 92 through 95 -until' afterthe second of the double marker pulses shown in waveform 147 has beenapplied to the advance windings 88 through 91, as shown in the waveform159. The set winding 92 is wound on the magnetic core 84 in a directionopposite to that in which the set'windings 93through 95 are wound on themagnetic cores 85 through 87,- respectively. The winding 92 is wound ina direction such that the reception of the delayed separated markerpulse causes the magnetic core 84 to be shifted into the onestate, asindicated by the raised portion of waveform 154; The status of themagnetic cores 85' through 87 in the zero state is confirmed by thereception of the delayed marker pulse at the windings 93 through 95.

At the same time that the delayed marker 'pulse is applied to the setwindings 92 through 95, the delayedv marker pulse is also applied overlead 123 to the left hand side of the multivibrators'117 through 119. As

shown in the multivibrator 117, the application of the positive markerpulse to the base electrode of transistor 124 causes transistor 124 tobe cut-oif and transistor 125 to conduct. As shown in the waveforms 151through one state in which it has been placed by the previous receptionof the delayed marker pulse and into the zero state. Since the magneticcores 85 through 87" are in a zero state at this time, the statusthereof is merely confirmed. The base winding 29, is wound in such adirection that a negative voltage is induced therein. The emitterelectrode becomes sufficiently more pos-. itive with respect to the baseelectrode to cause tram sistor 107 to conduct. V

Capacitor 110 is normally charged negatively with respectto ground in amanner to be described. -When 7 the transistor-1W begins toconduct,capacitor 110-.dis

charges and current'flowsiover' an electrical pathincludasses:

' electrical condition or one to beshifted outwo fthe in-ginpnawinding;102, collector. winding. 96 and 11 359. sistor 107: The voltage inducedin the collector winch. ing 96 results. in a more negative voltage beinginduced in the base winding 99. By this regenerative action; transistor'107 conducts more heavily, and the magnetic core 84 is made to assume azero state, as shown in waveform 154. The input winding 102 is wound onthe magnetic .core 85 in a direction such that the current flowing inthe input winding 102 during the period in which transistor107 isconducting functions to assist the current flowing in the advancewinding 8% due to the reception of the. first channel pulse in holdingthe mag-. netic core 85 in a zero state. i

When the magnetic core 84 has assumed. a zero state, the magneticcoupling therethrough drops substantially to zero and transistor 107ceases conducting.

Capacitor 110 charges through the resistor 111 fronu the negativeterminal of the battery 112. A currentrof oppositepolarity now flowsthrough the input winding;

1G2 and the current thereby flowing in the inputwinding 192 causes themagnetic core 85 to assume -a one.

state, as shown in waveform 155. The time constantD of the. resistor111-capacitor 110-transistor 197 network is set. according to thefrequency of the channelpulses so that the current reversal occurs afterthe channel pulse applied to the advance windings 88jthrough-91 atrailing edge whose time is determined according to t he time of thefirst channel pulse. In this manner, thepulse position modulated pulsereceived is converted into a, pulse width modulation pulse. The audiocomponent of the width modulation pulse is a function of the per centagedeviation of the trailing edge and pulse amplitude. T he low-pass filterwhich may. bean in; ductance-capacitance circuit of conventional designserves to integrate the current pulses applied thereto, producing anoutput signal according to the-audioco'mponent of the current pulse. Asignal is availablea't'theterminal 133 which is representative of themodulating signal energy r gi y pp ie y h ator a sampled by the magneticcore l1 transistor 42 circuit Qffthe ring counter given in Figure 3.

When the second time modulating channel pulse received, the singleelectrical condition or .one. isshifted from the magnetic core 85 to themagnetic coref,8. The magnetic core 86 is made to assume a one state, asshown in the Waveform 156. The multivibrator 118 is made to assume itsother stable state, and a width modulated current pulse having atrailing edgewhose time is determined by the time of the second'channel.v

pulse is applied to the low-pass filter 138. This action may bedetermined by a comparison of the Waveforms 147, 1 55 and 152 given inFigure 6. .Thetfilter 13 3 will function to integrate the current pulsesapplied th tea o as ermine by hs o i la nschana lmlssa. received toimakeavailable at the terminal 156 a signal repr s n e. of t modulating sigal; n y o i ina pplie y sen ra rfis and amp ed vthsmassstis.

a 2- anS S 6P uit 7f h inssquu s shqwn' irrFigure 3. In the samemanner,the receptionofithe,

third'time modulated channel pulsewillcause theseco m eti W & bs .mlilvi ra o l 1.1 Qwi l: produ e s a ies m tts a shown n. aveform .5.. hailing, @2 8 f tim r- 1s dete mines! w h? r the thirdchannet'pulse. Thelow-pass filter 141 will integrate the current pulses applied thereto,and a signal will be made available at the-terminal 139 which isrepresentative of the modulating signal energy originally supplied bythe generator 49 and sampled by the magnetic core 13-transistor 44circuit. A compact distribut ing-demodulating circuit arrangement foruse in a time division multiplex system is disclosed. By usingtransistors and magnetic cores to perform functions previously performedby other equipment, a circuit is providedwhich is characterized by lowpower consumption and the requirement of a minimum number of componentsof small size and weight. I

In theoper at'ion of the circuit arrangement given in Figure 5, as shownby the waveforms1151, 152 and 153 given in Figure 6, it may be seen thatthe duration of the widthmodulated pulses produced in the respectivemultivibrators '117 through 119' varies -from approxi- .mately thetimebetween two adjacentincoming pulses of the multiplex signal (for thefirst channel 1) to apthe width modulated pulsesproducedareall of thesame average width, approximately equalto the duration betweentwoyadjacent incoming pulses of the multiplex signal. Themain differencein thearrangement of Figure the distributing-(le a frequency: n timesthe frequency of the separated marker pulse, where n is'the number ofchannels in-the multiplex signal. .In the example given, the frequencyof the separated markerpulse would be multipled by four. I The .pulsegenerator 163 may be of any suitable type known in the art and mayinclude a transistor square or'sine wave oscillator to which areconnected the necessary pulse shaping and amplifying circuits. Theautomatic*frequency control circuit 164 may be of the type whichcompares the time of the pulses'produced by the generator 163 over lead165 with the time of the separated marker pulses; .If the generatedpulses are delayed or arrive early. with respect to the separated markerpulses, the circuit 164 functions to alter thetime of the pulsesproduced by the generator 163 by'a proper control signal fed over lead166 for each separated marker pulse received .untilthe' propersynchronisrn is obtained.

One'type of such circuit isthat called fly-wheel'sync in." Many examplesof such systems are television systems. available in the, art.

*The pulse train produced by the generator 163 is applied tothe seriesconnected advance windings'88 through 91 over an electrical pathincluding a delay line 167. The delayed pulse train isindicated inwaveform 168. The delay line 167 is set to delay the pulses in the traina sufiic'ient amount d to prevent the application 7 is the requirementofa localfo'scillatorcircuit which is lock e'd to the'marker-pulse ofthe incoming multiplex signal." The arrangementbf' Figure '5 do'esnotrequire 'such an oscillator circuit.--- f For ease of description,the circuit components in Figure 7 similar in constructionand'operationto circuit componentsin Figure 5 have been given the same referencenumerals; Referring to Figure 7; a magnetic core shiftregister includingthe magnetic core 84 through 87 is provided which is similar inconstructionand operation to the shift register shown in Figure 5. Theright hand side of the multivibrators"117'through 119 are.

connected to the outputcircuits of the'mag'netic cores- 84 through 86,respectively, over separate electrical paths including the respectivediodes 126, 129 and 131 in the manner-previously described. The'outputcircuits of the multivibrators, -'in this case-(from the'left hand side'thereof," are connected to the respective terminals 133, 136 and 139through the isolation circuits 134, 137 and 140 and the low-pass filters135, 138 and 141.

The operation of the circuit ar'rangement givenin Figure 7 will bedescribed in connection with the waveforms shown in Figure 8.The-incoming multiplex signal;

160 including the double marker'or synchronizing signal followed 'bythree time modulated pulses is applied to input terminal 106. 'The-marker' pulse separator 120 functions to produce a separated markerpulse in a manner previously described. The separated -.marker pulseshown in the waveform-161 is fed frornthe separator 120:"over twoseparate paths. The separated' marker pulse is fed over one electricalpath includinga lead162 and the. series-connectedfse't windings "92through 95. The current flowing in the winding 92 causes the magneticcore 84 to a'ssumea bne statehand the ,current fiow-j transistor 125 toconduct.

iiig in the windingsf93 through caus'es.themagnetie cores 85 through 87to.each:ass'um'e a,ZerolstateQThe; separated marker pulse isalso fed toan automiati'c fre quency control circuit 164.; The control circuit 164functions to compare the frequency of the generator 163,

with that of the incoming separatedmarker-pulse. .The generator 163 isdesigned to produce a pulsetrain having prevent the proper setting 7 3the -one state-by the separated marker pulse, since thecurrentfiowingrin'the .winding 88 'could tend to hold'the.

of a pulse of the generated pulse train and of the sepa-: rated markerpulse to themagnetic cores 84 throughacoincident condition would 87 atthe same time. Such of the magnetic core 84 in magnetic core 84 in thezero state. I

the waveform 168 is applied to thewindings' 88 through91, the magneticcore 84 is shifted-into a zero state. The status ofthe-magnetic cores-85through 87 in a zero stateis merely confirmed; The operation of thecircuit including transistor 107, capacitor and resistor 111 thereaftercauses magnetic core 85 to assume a one state in the manner previouslydescribed. During the above action,

the positive pulse produced by the conduction of tran-'.

sistor 107 is applied'to the right hand side or base electrode'oftransistor of multivibrator 117. Transistor IZSiscut-Qfi andtransistor 124 on theleft hand side of multivibrator 117 conducts. Atthis time, the multi-' vibrators"118, 119 will be set so that the righthand side thereof is conducting; the left hand side being cut-ofi.

The first-channel time modulated pulse of the incoming multiplex signalisfed over lead .123from terminal 106 to the base electrode oftransistor 124 or left hand side of multivibrator 117, as well as to theleft handrside ofmultivibrators'118 and 119. 'As the left hand side ofthe multivibrators 118,119 are cut-off at this time; a

the status thereof is merely confirmed. The applicationv of'the positivechannel. pulse to the base electrode of transistor 124 causes transistor124to be cut-off and A width modulated current pulse, as shown in thewaveform 169, is fedfrom the collector electrode'of transistor 124 tothelterminal 133 through the isolation circuit 134 and loW-pass'filter135.

The current pulse will have a trailing edge whose time varies accordingtothe timeof the received time modulated'pulse. 'Inother words, theduration of the resulting widthmodulated pulse will'be determined bythechange in condition of multivibrator 117 at the timethe first channelpulse is received. A signal will appearat the terminal133i-representative of the modulatingsignah 1 J I energysupplied bygenerator 47 andtransmitted over channel 2 of the multiplex signal.-

; The circuit operations upon the. reception of the channels. 3-- and 4timemodulated 'pulses willlbe' similar.

When the single. electrical conditioner one.is shifted.

from magneticjcore 85 to magneticscore86 by the next-*- pulse'applied'tothe advance windings188 through .91;

thauleft hand side of multivibrator. 1118 becomes conducting and theright hand side is cut-off. Upon the application of. the channel3"time'. modulated pulse. over lead 123, multivibrator 118 changes toitsother stable state. A width modulated current pulse is applied from themultivibrator 118 to the low-pass filter 138. having a trailing edgewhose time varies according to the time of the time modulated pulsereceived. As shown in waveform 170, the width of the pulse applied tothe low-pass filter 138 is a function of the time of the channel 3pulse. A signal will appear at terminal 136 representative of themodulating signal energy supplied by generator 48 andtransmitted overchannel. 3 'of the multiplex signal. c

The next pulse applied to the advance windings .88 through 87 will causethe single electrical condition or one to be shifted from the magnetic.core 86 to the magnetic core 87. Multivibrator 1'19. assumes its stablestate in which the left hand side is conducting and. its right hand sideis cut-ofi. Upon the applicationof the channel 4 time modulated pulseover lead 123, multivibrator 119 will assume its other stable state. Asshown in waveform 171, a width modulated current pulse having a trailingedge which varies according to the time of .the channel 4 pulse is fedfrom the multivibrator 119 .to the low-pass filter 141. A signalrepresentative of the modulating signal energy supplied by generator 49and transmitted over channel 4. of the multiplex signal will appear atterminal 139.

'In the operation of the circuit arrangement shown in both Figures 5 and7, the magnetic core shift register functions to steer. or direct theincoming time modulated pulses to the proper channels. and reliable inoperation. By using magnetic'cores and transistors, an improveddistributing-demodulating circuit is provided for use in a time divisionmultiplex modulation system. Such a system constructed according tov theinvention can be readily adapted for use, in tele-V metering or othersystems where size and weight, as well as low power consumption, areimportant factors.

Various modifications may be made to the circuit arrangements shown inFigures 5 and 7 without departingfrom the spirit of the invention.

circuits shown use the delay afforded by the resistance- .capacitancecircuit between magnetic cores, other types Although the brators 117through 119 in their proper stable state upon the startup of theequipment included in the inven.

tion. A test or starting signal may be applied to terminal 106 orsimilar means may be provided to accomplish this result.

An alternate means of demodulating the time modulated pulses, inconjection with the gating method described above, is to use a low-passfilter with an audio amplifierwhose response falls off with frequency at6'db. per octave. This converts the pulse position (or phase) modulationinto audio. In this way the multivibrator circuits may be dispensedwith. I

in certain applications, the ring counter shown in Figure 3 may beincluded in a system not requiring the production of a synchronizingsignal. The delay line 65 is disconnected and afurther signal generator172 may be connected to the magnetic core ltl'by winding 173. The firstchannel of the multiplex signal pro-. duced will include time modulatedpulses according to the modulating signal energy. supplied by the.generator 112. While both the. ring counterat the transmitting;

The circuits are simple.

end and the distributing demodulating circuit at the receiving end havebeen described as using P-N-P transistors, the invention is not limitedto the use thereof. NP-.N transistors of P type conductivity couldbeused by merely changing the'electrode connections and the polarity ofthe voltages supplied thereto in a known manner.

A four-channel multiplex system has been used in describing theinvention. The multiplex system, however, may be designed toinclude anynumber of channels by merely adding or subtracting the necessary numberof magnetic core stages in the ring counter at the transmitting end andthe shift register at the receiving end.

A transistor-magnetic core time division multiplex modulation system isdisclosed by the inventionwhich is characterized by the requirement of aminimum number of small components resulting in low power consumption,

providing a system readily adaptable for use many applications;

Having described the invention, I claim:

1. In combination, a first train of magnetic cores connected to form aring counter, a separate transistor regeneratively connected to each ofsaid magnetic cores, a separate source of modulating signal energyconnected to each of certain ones of said magnetic cores, means foroperating said, counter to sequentially sample during separate anddistinct time intervals the modulating signal energy supplied by firstone .jand then another of said sources, said counter functioning duringeach sampling interval to produce ,a modulated signal determined by themodulating signal energy sampled during said interval, an output circuitconnected to. all of said magnetic cores for combining said modulatedsignals in the order in which'they are produced to form a multiplexsignal for application over a single transmission path, a second trainof magnetic cores connected to form a shift register, a separatetransistor regeneratively connected to each of saidmagnetic cores. insaid second train, means connected to said path and responsive to saidmultiplex signal for causing said shift register to bring about thedistribution of said modulated signals amonga plurality ofdifferentchannels according to said order, each of said channels including meansresponsive to said modulated signals for applying to a utilizationcircuit an output signal representative of the modulating signal energysupplied by a corresponding oneof said sources.

2. In combination, a first train of magnetic cores connected to' form aring counter, a separate transistor regeneratively connected toeach ofsaid magnetic cores, a separate source of modulating signal energyconnected to each of certain ones of said magnetic cores, means foroperating said counter to first produce in each operating cycle thereofa synchronizing signal and to thereafter sequentially sample duringseparate and distinct time intervals the modulating signal energysupplied by first one and then another of said sources, said counterfunctioning during each sampling interval to produce a modulated signaldetermined by the modulating signal energy sampled during said interval,an output circuit connected to all of said magnetic cores for combiningsaid synchronizing andmodulated signals in the order in which they areproduced to form a multiplex signal for application over asingle.transmission path, a second train of magnetic cores'connected toform ashift register, a transistor regeneratively connected to. each of saidmagnetic cores in said second train, means connected to said path andresponsive to said multiplex signal .for causing said shift register tobring about the distribution of said and then another of said sources,said counter functioning during each'sampling interval to produce a timemodulated pulse determined by the amplitude'fof the modulating signalenergy sampled during 'saidinterval, an output circuit connected to allof said magnetic cores for combining said synchronizing signal andtimemodulated'pulses in the order in which they are produced to forma'multiplex signal for application over a single transmission path, asecond train of magnetic cores connected to form. a shift register, atransistor regeneratively connected to each of said magnetic cores insaid second 7 train, means connected to said path and responsive to saidmultiplex signal for causing said shift register to bring about thedistribution of said time modulated pulses among a plurality ofdiifere'nt channels according to said order and in synchronism with saidmultiplex signal,

each of said channels including means. responsiverto said 7 timemodulated pulses for applying 'to a utilizationcircuit an output signalrepresentativeof the modulating signal energy supplied byv acorresponding one of said sources. 7 4, .A coinbmation as 'claimedfinclaim 3 and wherein each'of said channels includes a bistable'multivibrator for converting said time vmodulated 'pulses' to widthmodulated pulses, andalow-pass filter'connectedfto said multivib'ra-torand responsive to the audio component of saidwidth modulated pulsestoproduce said output signal representative of vthe modulating signalenergy :supp'lied by a corresponding oneofsaid Sources;

5; In combination, a first tram of magnetic cores. connected to'form aring counter, a separate transisto'rregeneratively connectedto each ofsaid magnetic cores, a separate source of modulating signal energyconnected to eachof certain tones-of said magnetic-cores; meansforoperating said counter to'first produce in each operating cycle thereofa synchronizing signal and to thereafter sequentially sample duringseparate and distinct time interp,

vals the modulating signalenergy suppliediby first one and then anotherof said sources, said counter functioning during each sampling intervalto produce a time modulated pulse determined by the amplitude ofthernodulating signal energy sampled-during said intervah'an output vcircuit connected to allof said magnetic cores for com;

I bining said synchronizing signal and time =modulated pulses in theorder in. which they are produce dlto form a'multiplex signal forapplication over a singletransmis,

sion-ipath, a second train of magnetic cores lconnecte dto form a shiftregister, a separate transistor. regeneratively having a frequency equalto the f requency'of said;

connected to each of said magnetic cores ini'saids'econd channelincluding a bistable train, 1 a separate output the output circuit'of1each of multivibrator connected to saidmagnetic cores rn sa1dsecondtrain, a separator ci r- I cuit connected to said path, the outputof said .separator being connected to eachyof saidjmagnetic cores1nsaidsecond train and to each of said multivibrators, said separatorfunctioning in response tosaid synchronizing signal to cause the firstone of said magnetic cores in said second train to assume agivenelectrical condition-rand to'cause each of said multivibratorsgtobeset in the same given stable state,-means for connecting each' of saidmagnetic cores in said second train tjls'aid path andifor sequen-'tially operating said magnetic coresin saidfsecondtrain inresponse tosaid time modulatedpulses cause said said, time etic' w condition to beadvanced infsynchronisrn vvi modulated pulses from magnet c eore'; toniagn ,along said second train, each of said a t t suppliedbyqacorrespondingoneof saidf sources'. I multivibrfators being 7 'andwherem,'hich ,1; ga'eh or said tionship with ;said 5 synchro I lated pulsesfollowing said netic core to magnetic core in said second train eac itisconn'ect'ed' whem'saidfcondition aug r-tempura: that-magnetic core andinto "thenext'niagneti6 core-in said secondtrain'to assume its otherstable state,fand'a separate output' circuit connected to each ofsaidmulti vibrators and iiespons'iveto the, operation thereof to pro duce anoutput signal for application to a utilization *circuit representative'of'the modulating signal energy sup plied by a corresponding one ofsaid sources. H r a 6. A combination as claimed in claim S andwhereineach of said multivibratorsfunctions upon assuming said other stablestate to produce a width modulated pulse, a separate low-pass filterconnected to each of's'aidmulti vibrators, said filter being responsiveto the audio corn- 'ponent of "said width modulated pulses to producesaid each of certain ones of said magnetic cores, means for operatingoperating said counter to first produce in each cycle thereof asynchronizing "signal and to' thereafter sequentially sampleduring'separate and distincttimeiintewals the modulating signal energysupplied by first one .andthen another of said sources, said counterfunction:

ing during each samplingfintervaltoiproduce a'time' modulated 'pulsedetermined by the amplitude 'ofxthe, modulatingq'signal energy sampledduring *saidinterval,

an output circuit connected toxall of said magnetic cores foricombiningsaidsynchronizing signal and time modllr' flat'ed 'pulses" inpthe orderinwhich they are producedv :19

form a multiplex signal forapplication over'asingle transmission path, asecond train of magnetiecoresconnected to form 'a shift register, a;separatetransistor re "g'eneratively connected to each of saidmagneticcores in output channel including a.

saidjsecondrtrain, a separate bistable multivibrator connected to, theoutput circuitof each of said magnetic-cores in said second train, asepa; rator circuit connected to said path and to each of saidmagneticflcores in said second train, said separatorcir cuitbeingresponsive to said synchronizing signal to cause the first magnetic coreinsaidsecond train to-assume a given'electrical condition, a pulsegenerator connected to each of said magnetic cores in said second trainfor applying a pulse. train thereto, control means connected to saidseparator and to saidgenerator, said'control means being responsive tothe operation of said separator in response to said synchronizing signalto cause said-gene1f,-

ator to maintain said .pulse trainiin a synchronousjrela;

nizing signal, said pulse tram the number ofnsaid time modu.

chronizing signals times signalin said multiplex signal, reception,OfiSBld train causing said condition 'to said multivibrators beingresponsive to the operatic of v the magnetic coreto wh ch itisg dnnwq Wh9.. l,

dition is advanced out ofjthatirnagnetic core to assumeia given one-ofits stable statespineans for 'conri ectiiigfeach of said multivibratorsto saidpath, said multivibrators each being responsive hen placed insaid given stable 'stateto the-next tone-0'1: r

ceivd thereby to assume its other" stable -state;,yvhereb'y first oneand then another ofsaid multivibrators'are first made toiassume saidgiven stablestate' and thereafter said other stable state duringseparate and distinct time inter valsyand aseparate output circuitconnected to each ..of

said multivibrators andresponsive to the p on ther e V of to -produce anoutput signal for applicationto autili tion circuitrreprese tative ofthe'modulating s gnal ene p8 A scoinbinationias claimed in claim v r s sstiqns u ass last-mentioned synchronizing 7 said time modulated pulsesre.- p t other stable-state to produce a width modulated pulse having atrailing-edge whose time varies as a function of thetirne of the timemodulated pulse which causes said multivibrator to assume its otherstable state, and a separate low-pass filter connected to each of saidmultivibrators responsive to the audio component of said width modulatedpulses to produce said output signal representative of the modulatingsignal energy supplied by a corresponding one of said sources.

9. A time division multiplex communication system comprising, incombination, a first train of magnetic core circuits connected to form aring counter, each of said circuits including a transistorregeneratively connected to said magnetic core, separate individualsources of modulating signal energy singly connected over differentpaths to all but one of said magnetic cores, means for continuallyadvancing a single electrical condition from magnetic core to magneticcore along said train to place said magnetic core circuits in operationsequentially, said one magnetic core circuit being placed in operationeach time said condition is advanced from said one magnetic core to thenext magnetic core in said train by said means to produce asynuchronizing signal, said other magnetic core circuits beingsequentially placed in operation for separate and distinct timeintervals to each produce a modulated signal determined by themodulating signal energy supplied to the magneticcore therein duringsaid interval, a common output circuit connected to the output of eachof said magnetic core circuits for combining said synchronizing signaland said sequentially produced modulated signals into a multiplex signalfor transmission over a single transmission path, said counter producingever said transmission path in each operating cycle thereofasynchronizing signal followed in order by the modulated signals producedby first one and then another of said magnetic core circuits, a secondtrain of magnetic cores connected to form a shift register, atransistorvregeneratively connected to each of said magnetic cores in"said second train, means connected to said transmission path andresponsive to said multiplex signal for causing a single electricalcondition to be advanced from magnetic core to magnetic core along saidsecond train synchronously with said multiplex signal, said shiftregister functioning to cause the distribution of said modulated signalsamong a plurality of different channels according to said order in whichsaid modulated signals are received, each of said channels includingmeans responsive to said 'rnodulated signals for producing an outputsignal representative of the modulating signal energy supplied by' l'acorresponding one of said sources, and separate means included in eachof said channels for applying'said output signal to a utilizationcircuit.

It A timedivision multiplex communication system comprising, incombination, a first train of magnetic core circuits connected to form aring counter, each of said circuits including a transistorregenerativelyconnected to said magnetic core, separate individual sources ofmodulatingsignal energy singly connected over ditferent paths to all butone of said magnetic cores, means for continually advancing a singleelectrical condition from magnetic core to magnetic core along saidtrain to place said magnetic core circuits in operation sequentially,said one magnetic core circuit being placed in operation each time saidcondition is advanced from said one magnetic core to the next magneticcore in said train by said means to produce a synchronizing signal, saidother magnetic core circuits being sequentially placed in operation forseparate and distinct time-intervals to each produce a time modulatedpulse determined by the amplitude of the modulating signal energysupplied to the magnetic core therein during said interval, a commonoutput circuit connected to theoutput of each of said magnetic corecircuits for combining said synchronizing signal and said plex signalfor transmission over a single transmission path,-said counter producingover said transmission path in each operating cycle thereofasynchronizing, signal followed in order by the time modulated pulsesproduced by first one and then another of said magnetic co're'circuits,a second train of magnetic cores connected to form a shift register, atransistor regeneratively connected ,to each of said magnetic cores insaid second train, means connected to said transmission path andresponsive to said multiplex signal for causing a single electricalcondition to be advanced from magnetic core to magnetic core along saidsecond train synchronously with said multiplex signal, said shiftregister functioning to cause the distribution of said time modulatedpulses among a plurality of different channels according to said orderin which said modulated pulses are received, each of said channelsincluding means responsive to said modulated pulses for producing anoutput signal representative of the modulating signal energy supplied bya corresponding one of said sources, and separate means included in eachof said channels for applying said output signal to a utilizationcircuit.

11. A time division multiplex communication system as claimedin claim 10and wherein each of said channels includes a bistable multivibrator forconverting said time modulated pulses to width modulated pulses, and alowpass filter connectedto said multivibrator and responsive to theaudio component of said width modulated pulses to produce said outputsignal representative of the modulating signal energy supplied by acorresponding one of said sources.

12. A time division multiplex communication system comprising, incombination, a first train of magnetic core circuits connected to form aring counter, each of said circuits including a transistorregeneratively connectedto said magnetic core, separate individualsources of modulating signal energy singly connected over differentpaths to all but one of said magnetic cores, means for continuallyadvancing a single electrical condition from magnetic core to magneticcore alo'ng said train to place said magnetic core circuits inoperation, said one magnetic core circuit being placed in operationsequentially each time said condition is advanced from said one magneticcore to the next magnetic core in said train by said means to produce asynchronizing signal, said other magnetic core circuits beingsequentially placed in operation for separate anddistinct time intervalsto each produce aatirne modulated pulse determined by the amplitude ofthe modulating signal energy supplied to the magnetic core thereinduring said interval, a common output cirpath in each operating cyclethereof a synchronizing signal followed in order by the time modulatedpulses pro duced by first one and then another of said magnetic corecircuits, a second train of magnetic cores connected to form a shiftregister, a separate transistor regeneratively connected to each-of saidmagnetic cores in said second train, a separate output channel includinga bistable multivibrator connected to the output circuit of eachofsaid'magnetic cores in said second train, a separator circuit connectedto said transmission path, the output of said separator being connectedto each of-said magnetic cores in said second train and to each of saidmultivibrators, said separator functioning in response to saidsynchronizing signal to cause the first one of said magnetic cores insaid second train to assume a second given electrical condition and tocause each of said mullZlVlbl'EttOlS to be set in the same given stablestate, means for connecting each of said magnetic'cores in said secoiidtrain ,to said transmission path'and for sequentia1lyioperating saidmagneticcores in said second train in response te said'tim'e; modulatedpulse-s te cans'e' 'saidsecbnd co'n ditioni'to" be advanced'in'synchronisni with 'saidmodu- Ia'ted pulses from magnetic core tomagneticcore along said second train, each of said multivibrators beingresponsive to the operation of the magnetic coreto which it is connectedwhen said second condition is advanced out of, that magnetic'core andinto the next magnetic core in said second train to assume its otherstable state, and a separate output circuit connected to each of saidmultivibrators and responsive to the operation thereof to, produce anoutput signal for application to a utilizat'ion circuit representativeof the modulating signal energy supplied by a corresponding one of saidsources; e

' 13. A time division multiplex communication system comprising,in'combination, a first train of magnetic core 'circuits connected toform a ring counter, each of said circuits including a transistorregeneratively connected to said magnetic core, separate individualsources of modulating signal energy singly connected over differentpaths to all but one of said magnetic cores, means for continuallyadvancing a single electrical condition'from magnetic core to magneticcore along said train to place said magnetic core circuits in operationsequentially, said one magnetic core circuit being placed in operationeach time said condition is advanced from said one magnetic core to thenext magnetic core in said train by said' means. to produce asynchronizing signal, 'saidother magnetic core circuits beingsequentially placed in, o e'r-J I ation for separate and distinct timeintervals to each producesa time modulated pulse determined by thevapulses, into amultiplex signal for 'transmission ovala v'saidsynchronizing signal and sequentially produced time, '30, plitudeof the modulating signaleenergy supplidi'o the 'magnetic core thereinduring said interval, a common output circuit connected .to'the outputofeach of said magnetic core circuits for combiningsaid synchronizing-Signal and said sequentially produced time modulated singletransmission" path, said. counter producing over f i said transmissionpath in each operating cycle thereof a synchronizing signal followed inorder by thetime modulated pulses produced by first one and then anotherof'said magnetic core'circuits, a second train of I magnetic coresconnected to form a shift-jregister', a separate transistorregeneratively connected to each'of said magnetic cores in said secondtrain,a separate output channel including a bistable multivibratorconnected to the output circuit of each of said magnetic cores in saidtrain, a separator circuit connected to, said transmission path and toeach of said magnetic cores in said second train, said separator circuitbeing responsive to said synchronizing signaltocause the first magnetiecore stable fstatei and thereafter said {other- 'stabl'e state duringseparate and distinct'timeintervals, and a separateizoutsput circuitconnected to each of said multivibrators and responsive to the operationthereof toproduce anoutput signal for application to a utilizationcircuit IePresentative .of the modulating signal energy supplied bya-corj responding one or said sources. o I 14; A time division multiplexmodulator comprising, in combination, a train of magnetic core circuitsconnected .to form a'ring counter, each of said circuits in-.'

''cluding a single transistor regeneratively connected to said magneticcore, separate individual sources of modu"-: lating signalenergy singlyconnected over different paths to all butone of said magnetic cores,means for'continually advancing a single electrical conditionfrommagnetic core to magnetic core along said train to place saidmagnetic core circuits in operation sequentially; means connected tosaid one magnetic core circuit and responsive to the operation thereofeach time "said C0111 dition is advanced from 'said one magneticcore tothe next magnetic core in said train to produce a synchro-i nizingsignal, said other magnetic core circuits being sequentially placed inoperation for separate'an'ddistinct time intervals to each produce atime modulated pulse determined by the amplitude of the modulatingsignal energy supplied to the magnetic core therein duringlsaid" sionover-a single transmission path. a

1'5. A time division multiplexmodulator comprising;

in combination, .a train of magnetic core circuits con? nected 'to form:a ring counter, said magnetlc coresbeing characterized by an abruptchange in flux density when the magnetizingforce exceeds a threshold.value, eachof said circuits including a'single transistora-regeneraetively connected to said magnetic core,; separatejindi i' vidual sourcesof modulating signal energysingly fcon nected over difierent paths toall but one of said magnetic cores, means to supply a series of sawtoothwaves to said magnetic cores for continually advancing single felectrical'condition from magnetic core to magnetic-core in said secondtrain to assume a second givenffelectrical condition, a pulse generatorconnected to'each of said magnetic cores in said second train forapplying a pulse train, thereto, control means' connected'to saidseparator and to said generator, said control means beingfresponsaidsynchronizing signal tocauseifsaid generator to maintain said pulsetrain' in 'synchronism Withtsaidsynalong, said train to place saidmagnetic core circuits'iin operation sequentially, means connected tosaid one mag netic core circuit'and responsive to the operation thereofeachftimesaid condition is advanced from 'saidjone magnetic 'core'to-thenext magnetic core in-said train to produce a synchronizing signal, saidother magnetie corefcircuits being-sequentially} placed in operation forseparate 'and distinct timeintervals ,to each. produc'e jatime'modulated pulse determined by the time at vvhich the'amplit'udeotthe modulating signal'ene'rgywsupplied to themagnetic core thereinduringfs'aidjintervalplus 'sive tothe operation of said separator'inresponse to a 'the amplitude of the sawtooth suppliedto said last-me'n-ta tioned magnetic core exceeds said threshold value, a

common ,output circuit'connected to thefoutp ut of each I of said 7magnetic core circuits for combining 7 saidsyn chronizing signal andsequentially-produced time modu- 60v a single'transmission path.

lated pulses 'into a r'nultiplex signalfor transmission pver "l6.' In afimedivision'multiplex communication sysgtem, afrnultiplex'modulatorcomprising, in combination;

condition is advanced out of that magneticcore'to lassume. a givenloneof its stable states, meanslfor con-r necting each of saidmultivibrators to said transmission j path, said multivibrators eachbeing responsive When placedin said given stablestateto thejnext oneofsaid other stable state, wherebyfirst one and then another; of saidmultivibrators are first made to assume said given;

' time modulated pulses received thereby to assume its a train ofmagnetic corecircuits connected to form a ring counten'each of saidcircuits including a singletransistor regeneratively connected to saidmagnetic core, separate individuaL-sources of modulating sign'alenergy-singly connected over different 'pathSEtoQaIlbut one -of' said:

magnetic cores, means for continuallyadvancing a si'ngl'eelectricallconditionfrom magnetic coreto magnetic core along said trainto place saidmagnetlc core circuits in operation sequentially, meansconnected to. saidone mag-- etic' core circuit and responsive to theoperation thereof each time said condition is advanced from'isaid onemagnetic core to the'nex-t magnetic core in said train'to prov.

duceia svr hmnizinesignal; said oth r ma neti (29K? circuitsheingsequentially placed inoperation foe separate and distincttime intervalsto each produce a time rnodulatedpulse determined. by the amplitude ofthe modulatin-g, signal energy supplied to the magnetic core thereinduring said interval, a common output circuit connected to the output ofeach oflsaid magnetic core circuits for combining said synchronizingsignal and sequentially produced time modulated pulses into a multiplexsignal for transmission'over a single transmission path, and meansconnected to said transmission path and responsive to said multiplexsignal for distributing said time modulated pulses among a plurality ofchannels according to the order in which said time modulated pulses arereceived, each of said channels including means responsive to said timemodulated pulses to produce an output signal for application to autilization circuit representative of the modulating signal energysupplied by a corresponding one of said sources.

17. A time division multiplex demodulator comprising, in combination, aninput terminal to which is applied a multiplex signal including in eachframe a synchronizing signal followed by the same number of seriallyappearing time modulated pulses, a train of magnetic cores connected toform a shift register, a separate transistor regeneratively connected toeach of said magneticcores, a separate output channel including abistable multivibrator-connected to the output circuit of each of saidmagnetic cores, a separator circuit connected to said terminal,

to said multivibrator and to each of said magnetic cores,

said separator functioning in response to said synchronizing signal tocause the first one of the magnetic cores in said train to assume a.given electrical condition and to cause each of said multivibrators tobe set in the same given stable state, means connected to said terminaland to all of the said magnetic cores responsive to said time modulatedpulses, to cause said condition to be advanced in ,s'ynchronism withsaid pulses'from magnetic core to magnetic core along said train, eachof said multivibrators being'responsive to the operation of the magneticcore to which it is connected when said condition is advanced out ofthat magnetic core and into the next magnetic core in said train toassume its other stable state, and a separate output circuit connectedto each of said multivibrators and responsive to the operation thereofto produce an output signal for application to a utilization circuit.

18. A time division multiplex demodulator as claimed in claim 16 andwherein each of said multiviorators functions upon assuming said otherstable state to produce a Width modulated pulse, a separate low-passfilter connected to each of said multivibrators and responsive.

to the audio component of the width modulated pulses appliedthereto toproduce said output signal for application to a utilization circuit.

19. A time division multiplex demodulator comprising, in combination,atrain of magnetic cores connected to form a shift register, a separatetransistor regeneratively connected to each of said magnetic cores, aseparate output channel including a bistable multivibrator connected tothe output circuit of each of said magnetic cores, an input terminal towhich is applied a multiplex signal including in each frame asynchronizing signal followed by the same number of serialiy-appearingtime modulated pulses, a separator circuit connected to said terminaland to eachof said magnetic cores, said separator circuit beingresponsive to said synchronizing signal to cause the first magnetic corein said train to assume a given electrical condition, a pulse generatorconnected to each of saidmagnetic cores for applying a pulse train hereo, control means co nected to said. transistor. and to sa d ene ato sa cntro means b s e pcn iv t0 e. pe n of s id s p ra or n esp nse o s d 3!.chronizin'g s n o aus sa d ge rat to ntai said pulse train in a propersynchronous relationship with said synchronizing signal, said pulsetrain having a frequency equal to the frequency of said synchronizingsignal times the number of time modulated pulses following saidlastmentioned synchronizing signal, the reception of said pulse traincausing said condition to be advanced from magnetic core to magneticcore along said train, each of the mutivibrators being responsive to theoperation of the magnetic core to which it is connected when saidcondition is advanced out of that magnetic core and into the next insaid train to assume a given one of its stable states, means forconnecting each of said multivibrators to said terminal, saidmultivibrators-each being responsive when placed in said given stablestate to the next one of said time modulated pulses applied thereto fromsaid terminal to assume its otherstable state, whereby first one andthen another of said multivibrators are madeto assume said given stablestate and thereafter said other stable state during separate anddistinct time intervals', and a separate output circuit connected toeach of said multivibrators and responsive to theoperation'thereof toproduce an output signal for application to a utilization circuit. l i l20. A time division multiplex demodulator as claimed in claim 19 andwhereineachof said multivibrators functions to produce upon each-changefrom said given to said other stable state a width modulated pulse, asep arate low-pass filter connected to each of said vibrators andresponsive tofthe audio component of's'aid width modulated pulses toproduce said outputv signal.

21. In combination, a train of magnetic core circuits connected toform aring counter, said magneticcores being characterized by an abruptchangein flux density when an applied magnetizing force exceeds athreshold value, each of said circuits including a transistor regeneratively connected to said magnetic core, separate individualsources of modulating signal energy singly connected over diiferentpathssolely to said magnetic cores, means to supply a series of sawtoothwayes to said magnetic cores for continually advancing a singleelectrical condition from magnetic core to magnetic core along saidtrain to place first one and then another of said magnetic core circuitsin operation, said magnetic core circuits being sequentially placed inoperation for separate and distinct time intervals to each produce inturn at the output of said transistor a time modulated pulse determinedby the time at which the amplitude of the modip lating signal energyplus the amplitude of, the sawtooth supplied to the magnetic corethereinduring said interval exceeds said threshold Value, a common outputcircuit connected to theoutput of the transistor in each of said.magnetic core circuits for combining said sequentially produced timemodulated pulses into a multiplex signal for transmission over a singletransmission path.

References Cited in the file of this patent UNITED STATES PATENTS V 7Pawley Q Dec. 10, 1957

